Leveraging the use of herbarium collections in modern systematics—examples from Pteridology
Nagalingum, Nathalie , Lupia Ii, Richard , Pryer, Kathleen M. .
The importance of paleobotanical and herbarium collections in understanding the evolution of heterosporous ferns.
While herbarium collections conserve the record of recent biodiversity, repositories of paleobotanical collections preserve the history of plant evolution spanning millions of years. Together, these collections have the potential to inform our understanding of the changes in diversity and morphology through time. Here we use molecular data together with morphological data assembled from herbarium specimens as well as the fossil record to infer the history of Salviniales, a small group (~ 100 species) of heterosporous ferns that are well-nested within a large clade (~10,000 species) of homosporous, leptosporangiate ferns. Fossils of Salviniales reveal unique combinations of morphologies that are no longer observed in extant species, allowing us to infer pleisiomorphies, and thus, the sequence of morphological evolution in the group. Fossils of Salviniales are also applied as calibrations in a molecular phylogeny of living species to obtain dated trees. Our timetree documents a Paleogene radiation in Salviniaceae and a more recent Neogene diversification of Marsileaceae. We also use the timetree to detect shifts in diversification rates. On the other hand, a compilation of the megaspore fossil record for heterosporous ferns indicates elevated species diversity in the Cretaceous—a signature that is not obtained using molecular data alone. Thus, the perceived long “phylogenetic fuse” observed in the Salviniales is not due to low diversity, but rather due to the extinction of early lineages and the inability of molecular data to detect extinct lineages. However, the fossil record is not without its own biases, because the recent diversification in Marsileaceae is not reflected by the fossil megaspore data that have been recovered. Our results show that the combination of data preserved in both herbarium and fossil collections are critical if we are to achieve a more complete understanding of the history of life on earth.
Log in to add this item to your schedule
1 - University of California, Berkeley, Integrative Biology, 3060 Valley Life Science Building, MC# 3140, Berkeley, CA, 94720, USA
2 - Sam Noble Ok Museum Natural History, University of Oklahoma, 2401 Chautauqua Avenue, Norman, Oklahoma, 73072, USA
3 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Ballroom C/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 11:10 AM